A principle of emitting electrons is largely divided into thermal emission and field emission. Among them, recently, a lot of researches for the field emission have been conducted. A principle of the field emission is to emit electrons from an emitter when an electric field is applied to a conductive emitter in vacuum and recently, a material which has recently been in the limelight as an electron emission source (emitter) is a carbon nanotube (CNT). Since the CNT has a geometric structure with low work function and a high aspect ratio, a field emission factor is very large. Accordingly, the electrons may be easily emitted under a low electric field. A method of forming the CNT as an emitter on an electrode is a method in which the CNT is fabricated in a paste form to be screen-printed on a substrate and the method has advantages in that fabrication cost is low and mass production is possible.
Meanwhile, FIG. 1 is an enlarged cross-sectional view of an emitter formed by coating a CNT paste made by adding metallic particles having micrometer or nanometer sizes on an electrode substrate, in order to increase adhesion between a CNT emitter and a cathode electrode. The geometric characteristic of the CNT due to the high aspect ratio may be a large advantage as the emitter, but may be a disadvantage in that the CNT is hardly evenly dispersed with uniform density. Currently, various methods has been proposed as a method of dispersing the CNT, but since the process is complicated and although the dispersion is sufficient, dispersity becomes easily deteriorated again during a paste fabricating process and as a result, there is a problem in that the CNTs are reaggregated. Due to the problem, the CNTs are partially concentrated as shown in FIG. 1A in the implemented CNT emitter to deteriorate uniformity and prevent electron emission due to a screen effect and as a result, the emitter characteristic is deteriorated.